Biological Explanations Of Schizophrenia

Question 1

Genetic explanation

Answer 1

trying to find a gene responsible for causing schizophrenia (if found it could lead to early detection and prevention of schizophrenia).

Question 2

Concordance rates for schizophrenia

Answer 2

General population: 1%
Adoptees: 6.7%
DZ twins: 17%
MZ twins: 48%

Question 3

Candidate gene

Answer 3

• there is not one ‘schizophrenia gene’
• schizophrenia is polygenic and aetiologically heterogenous

Question 4

Polygenic meaning

Answer 4

• caused by more than one gene

Question 5

Aetiologically heterogeneous meaning

Answer 5

different combinations of factors (e.g genetic, environmental) are required and can lead to the condition.

Question 6

Mutations explanation

Answer 6

• schizophrenia can have a genetic origin without a family history due to a mutation in parental dna.
• evidence comes from a study that found correlation between paternal age and risk of schizophrenia due to increased chance of sperm mutation.

Question 7

Neural correlates: hyperdopaminergia

Answer 7

Hyperdopamiergia is too much dopamine in the subcortex. This affects central areas of the brain, including the Broca’s area (responsible for speech production), therefore it is associated with speech poverty and many positive symptoms such as hallucinations and delusions.

Question 8

Neural correlates: Hypodopaminergia

Answer 8

Hypodopaminergia is too little dopamine in the pre-frontal cortex (responsible for decision making), meaning it is associated with negative symptoms such as avolition.

Question 9

AO3: ripke et al study (support for neural correlates and candidate genes)

Answer 9

• conducted a huge study using previous data of 37,000 patients with 113,000 controls. 108 genetic variations associated with increased risk of developing schizophrenia were identified. Many of these coded for the dopamine neurotransmitter, providing supporting evidence for the dopamine hypothesis with reference to neural correlates, as well as candidate genes and the polygenic nature of schizophrenia.

Question 10

Parkinson’s (AO3 OR AO1)

Answer 10

Parkinson’s’ sufferers have low levels of dopamine.
• L-dopa raises DA activity
• people with Parkinson’s develop schizophrenic symptoms if they take too much L-dopa.
Suggests that dopamine could be associated with the development of schizophrenia.

Question 11

+ strong evidence base

Answer 11

+ Gottesman (1991) family study shows how genetic similarity and shared risk of schizophrenia are closely related.
+ Adoption studies Tienari (2004), show biological children of people with schizophrenia are still at heightened risk of schizophrenia even if adopted into a family without a history of schizophrenia.
+ Hiker et al (2018) – 33% concordance for Mz and 7% for Dz twins

Question 12

AO3: NEGATIVES -

Answer 12

• This explanation is reductionist as it reduces the complex disorder of schizophrenia to a basic cellular and chemical level which does not recognise the gender and cultural differences that occur.
• if the development of schizophrenia was purely genetic based, MZ twins should have 100% concordance rates due to sharing 100% of dna therefore it could be SLT and personal experience that lead to schizophrenia, so we can’t disentangle environmental causes and biological causes.
• Psychological risk factors include childhood trauma e.g. 67% with Sz (38% matched controls) reported at least one childhood trauma (Morkved et al 2017). This means that genes alone cannot provide a complete explanation for Sz